1. Field of the Invention
This invention is directed to flexible applicators for applying an oil-in-water emulsion in which allantoin has improved stability, particularly for cosmetic and over-the-counter drug applications.
2. General Background and State of the Art
Allantoin is a commonly used ingredient in cosmetic applications, particularly for skin creams, where it exerts a skin protective function. Many such cosmetic compositions are prepared as emulsions, particularly oil-in-water emulsions. One emulsifier system used with such compositions is a combination of sodium lauryl sulfate and beeswax. Although solutions of sodium lauryl sulfate are alkaline with an approximate pH of 9.5, the simultaneous use of beeswax with its organic acids produces a complex and neutralized system with a pH of about 6.8 to about 7.5. However, in such a system with a pH range of 6.8 to 7.5, allantoin degrades significantly with time in an accelerated stability test at 40° C. Because cosmetics are typically stored by users at room temperature, and room temperatures can fluctuate with climatic conditions, such a degree of instability is undesirable. Therefore, there is a need for an oil-in-water emulsified composition containing allantoin that uses the sodium lauryl sulfate-beeswax emulsion system in which the stability of allantoin is increased.
Moreover, there is a need for efficient and readily accepted applicators for such emulsions. The direct manual application of such emulsions to the skin of a patient can be messy and inefficient, and even health care professionals may be reluctant to perform such application to the skin of a patient who has open sores and is suffering from a blood-borne communicable disease such as AIDS or hepatitis C, to name only two of a number of such conditions. Accordingly, there is a particular need for an applicator that can apply such emulsions reliably and reproducibly to the skin of a patient. There is a further need for an applicator that can retain the emulsion on the skin of a patient for the desired time period.